102,933 research outputs found
The Riemann zeta function as an equivariant Dirac index
No full textAbstract. In this note an interpretation of Riemann’s zeta function is provided in terms of an R-equivariant L^2 -index of a Dirac-Ramond type operator, akin to the one on (mean zero) loops in flat space constructed by the present author and T. Wurzbacher. We build on the formal similarity
between Euler’s partitio numerorum function (the S^1 -equivariant L^2 -index of the loop space Dirac-Ramond operator) and Riemann's zeta function. Also, a Lefschetz-Atiyah-Bott interpretation of the result together with a generalisation to M. Lapidus’ fractal membranes are also discussed. A fermionic Bost-Connes type statistical mechanical model is presented as well, exhibiting a “phase transition at (inverse)
temperature β = 1”, which also holds for
some “well-behaved” g-prime systems in the sense of Hilberdink-Lapidus
Response of Slender Blocks Subjected to Seismic Motion of the Base: Description of the Experimental Investigation
No full textErectile dysfunction: expectations beyond phosphodiesterase type 5 inhibition
No full textIn the last few years the pathophysiological mechanisms of erection have been partially clarified, and the molecular machinery of the cellular components of the corpus cavernosum (CC) has been widely investigated. Since erection is a vascular event and the penis is a vascular organ, there must be an intact endothelium for an erection to occur. The regulation of penile tumescence inside the CC involves a balance between contracting and relaxing factors which regulate the functional state of smooth muscle cells. Recent studies have highlighted the importance of new local factors (i.e. phosphodiesterases, rho-kinases and endothelins), and pharmacological agents are available in the armamentarium of the specialist which are targeted to modulate the function of those mediators of erection. It is now well understood that male erectile dysfunction (ED) is a symptom rather than a disease; for this reason in the near future both general practitioners and specialists in internal medicine would have to interplay with sexual medicine. This review is intended to give the clinician some basic concepts of the pathophysiology of erection with relevance to the clinical practice, and to discuss the newest therapeutic approaches for those patients who do not respond to the treatment with oral inhibitors of phosphodiesterase Type 5
Effects of vardenafil administration on intravaginal ejaculatory latency time in men with lifelong premature ejaculation
No full textPremature ejaculation (PE) is thought to be the most common male sexual dysfunction; however, the prevalence of lifelong (LL)-PE is relatively low. The aim of this study was to investigate the effects of on-demand vardenafil (10 mg) to modify the intravaginal ejaculatory latency time (IELT) in men with LL-PE without erectile dysfunction. Forty-two men (18-35 years) were enrolled in a 16-week, double-blind, placebo-controlled, cross-over study. Primary end point was the modification from baseline of IELT assessed by stopwatch technique; secondary end points were post-ejaculatory refractory time (PERT) and variations of scores at the Index of Premature Ejaculation questionnaire. The changes in geometric mean IELT were superior after taking vardenafil (0.6 +/- 0.3 vs 4.5 +/- 1.1 min, P < 0.01), compared with placebo (0.7 +/- 0.3 vs 0.9 +/- 1.0 min, ns). PERT dropped significantly after vardenafil (16.7 +/- 2.0 vs 4.3 +/- 0.9 min, P < 0.001), compared with placebo (15.3 +/- 2.2 vs 15.8 +/- 2.3 min). Patients who took vardenafil (vs placebo) reported significantly (P < 0.01) increased ejaculatory control (6 +/- 2 vs 16 +/- 2), improved overall sexual satisfaction (7 +/- 2 vs 15 +/- 1) and distress (4 +/- 1 vs 8 +/- 1) scores, respectively. Multiple regression analysis (r(2) = 0.86) for IELT by the number of attempts at sexual intercourse showed significant differences between the slopes of lines for placebo and vardenafil (P < 0.0001). The most common adverse events for vardenafil (vs placebo) were headache (10 vs 3%), flushing (12 vs 0%) and dyspepsia (10 vs 0%), which tended to disappear over the time. In conclusion, in our study, vardenafil increased IELT and reduced PERT in men with LL-PE. Besides, improvements in confidence, perception of ejaculatory control and overall sexual satisfaction were reported. International Journal of Impotence Research (2009) 21, 221-227; doi: 10.1038/ijir.2009.21; published online 28 May 200
Response of Slender Blocks Subjected to Seismic Motion of the Base: Experimental Results and Initial Numerical Analyses
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